1. Field of the Invention
The present invention is directed to a process for making methyl iodide. More particularly, the instant invention is directed to a process for making methyl iodide by separately introducing methane and a source of oxygen into a molten salt comprising a metal iodide and a catalyst comprising a metal of Group IB or Group VIII of the Periodic Table of the Elements.
2. Background of the Prior Art
Methyl iodide is an important compound having many important uses. For example, methyl iodide is an excellent promoter in catalytic carbonylation reactions. In addition this compound is an effective methylating agent. It is also used in the synthesis of organometallic compounds used as intermediates in further organic synthesis. Methyl iodide, moreover, is a potential intermediate in the direct synthesis of hydrocarbons, such as ethylene, ethane and higher saturated and unsaturated aliphatic hydrocarbons. Those skilled in the art are aware that ethylene and higher alpha-olefins are building blocks in the synthesis of important commercial products such as plastic and rubber polymers.
Processes for the production of methyl iodide are known in the prior art. One such reference which teaches a process for converting methane to methyl iodide, however unsuccessfully, is provided in Broadbent et al., Trans. Faraday Soc., Vol. 67 (Pt. 10), 3030-3037 (1971). Broadbent et al. reported the formation of trace amounts of methyl iodide by the photochemical reaction of methane and iodine. The low yield of this reaction was attributed to the instability of the carbon-iodine bond.
U.S. Pat. No. 4,523,040, issued to Olah, describes a process for halogenating methane to produce methyl halides. This process involves the use of elemental chlorine or bromine in the presence of a solid acidic or metal catalyst.
Gorin et al., Ind. Eng. Chem., 40, 2128-2134 (1984) report the chlorination of methane with copper chloride-potassium chloride melts using a hydrogen chloride-air mixture in the absence of any basic salt to provide methyl chloride.
Other methods for producing methyl iodide are known, however, none of these conventional prior art processes involve a successful synthesis of methyl iodide from methane. Kirk and Othmer, "Encyclopedia of Chemical Technology," Third Edition, Vol. 13, 668, John Wiley and Sons, New York (1971) disclose that methyl iodide may be prepared by the reaction of methanol with phosphorus and iodine. In addition, methyl iodide may be produced by the reaction of dimethyl sulfate with an aqueous iodine slurry containing a reducing agent such as powdered iron or sodium bisulfite. In another conventional process methanol is reacted with hydriodic acid to produce methyl iodide. The reaction of potassium iodide with methyl p-toluenesulfate also forms methyl iodide. Other known reactions to produce this compound, as set forth in Kirk and Othmer, is the reaction of methylphenylether with iodine in the presence of aluminum. Finally, methyl iodide may be formed in high yield by the reaction of methanol with iodine and diborane. Although these processes result in the formation of methyl iodide none of these processes produce methyl iodide from methane in commercially significant yield.